This invention relates generally to article counting apparatus and more particularly to sensing and indicating apparatus for counting a plurality of substantially identical objects stacked adjacent to one another and either with or without spaces intervening between objects. More specifically, this invention relates to improvements with respect to the article counting apparatus disclosed by SAMUEL P. WILLITS and WILLIAM L. MOHAN in U.S. Pat. No. RE 27,869, reissued Jan. 1, 1974. The improvements of this invention relate to novel means to achieve signal enhancement and pitch matching utilizing a single sensor in the optical system and use of an electrical delay line to achieve the equivalent of a pitch matched variable width, half-line, single-line or multi-line pair sensor.
In the aforementioned WILLITS et al. patent, there was described apparatus for counting the plural stacked objects it was desired to count. In particular, maintenance of particular relationships between effective sensor size and stacked object size and particular circuitry combined under the conditions described in that application made high speed counting of plural stacked objects feasible, even where relatively low contrast gradients between adjacent ones of the stacked objects was encountered. The WILLITS, et al., specification further discussed several means of achieving signal enhancement for conditions where low contrast gradients were encountered. Each of the signal enhancement methods of that application in essence provided for matching of effective sensor width to the pitch of the stacked objects. Additional signal enhancement was provided by paired plural sensor arrangements, electrically connected in push-pull arrangements.
While the apparatus of the earlier WILLITS, et al, patent solved many problems, and in most instances provided an excellent method for stacked object counting, because the effective width adjustment of the sensor, sensor pairs or arrays was achieved by adjusting the physical size and/or the optical configuration of the sensor arrangement to the pitch of the stacked objects, it was difficult to obtain the pitch adjustment to the desired degree of accuracy over a wide range of pitch widths. Further, because of the sharp edge characteristics of the sensors employed in the earlier patent, unwanted higher harmonics of the desired signal frequencies occurred as the sensor passed over discontinuities in the objects being scanned.